糙米酚类物质对米淀粉消化特性的影响机制

Postprandial hyperglycemia has many serious hazards and can eventually cause type 2 diabetes mellitus, which some have called “postprandial diabetes”. Digestion of carbohydrates from food (especially for starch) is the major source of postprandial hyperglycemia. Therefore, delaying the digestion of carbohydrates in food could be an effective measure to prevent postprandial hyperglycemia and would decrease public expenditure of medical treatment. Phenolic components, which will be purified and identified from brown rice, can be used to decrease the digestibility of rice starch, and the functional mechanism will be investigated by in vitro models. The contents are described as follows: These extracts of phenolic components from brown rice will be enriched by chromatographic fractionation and their structures will be identified using LC-ESI-MS. The in vitro model will be made from phenolic components of brown rice, rice starch and digestive enzymes. The effect of phenolic components on physicochemical properties and digestibility of rice starch will be evaluated in various environmental conditions. The reaction characteristic and mechanism of phenolic components on the digestibility of rice starch will be revealed via kinetics of digestive reaction and molecular interaction between starch and phenolic components during the in vitro model. This study can significantly promote the development of controlling digestibility of starch in food.

餐后高血糖症有很多严重危害并能引起II 型糖尿病, 食品中碳水化合物尤其是淀粉的消化吸收是引起餐后高血糖症的主要原因，降低食品中淀粉的消化速率对于预防II 型糖尿病等慢性疾病、减少公共医疗支出具有重大意义。本项目利用糙米酚类物质控制大米淀粉的消化速率，纯化并鉴定其结构，通过模型体系揭示其作用机理。内容包括：采用不同溶剂萃取结合色谱分离技术富集糙米酚类物质，利用LC-ESI-MS鉴定其组成；用糙米酚类物质、大米淀粉、消化酶建立酚类物质-淀粉体外消化模型体系，研究不同环境条件下酚类物质对大米淀粉分子结构、分子量分布等基本物化性质及消化速率和消化率的影响，结合模型体系中消化反应动力学及酚类物质与淀粉分子之间的相互作用，揭示酚类物质对大米淀粉消化性质的作用机理。该研究将对有效控制食品中淀粉的消化性质起到推动作用。

餐后高血糖症有很多严重危害并能引起II 型糖尿病。食品中碳水化合物尤其是淀粉的消化吸收是引起餐后高血糖症的主要原因，降低食品中淀粉的消化速率对于预防II 型糖尿病等慢性疾病、减少公共医疗支出具有重大意义。. 本项目采用糙米酚类物质控制大米淀粉的消化速率。HPLC-MS鉴定结果表明，糙米酚类物质主要由酚酸、黄酮和花青素等酚类物质组成，且糙米酚都具有较强的抗氧化活性。构建了糙米酚-消化酶-淀粉模拟消化体系，在模拟消化体系中研究了提取的糙米酚类物质与消化酶相互作用对米淀粉消化性质的影响。结果表明，糙米酚类物质对ɑ-淀粉酶和ɑ-葡糖苷酶活性具有抑制作用，且糙米结合酚对ɑ-淀粉酶和ɑ-葡糖苷酶酶活的抑制率高于糙米游离酚。糙米酚均可使ɑ-淀粉酶和ɑ-葡糖苷酶的荧光强度降低，酚浓度越大荧光强度越弱，可能原因是糙米酚与消化酶由于氢键等作用形成基态复合物，从而抑制酶活。. 研究了糙米酚与米淀粉的相互作用对米淀粉分子结构及糊化、老化的影响。DSC糊化和回生率、X-射线衍射重结晶度分析、FTIR结晶区与非结晶区比值分析、SEM对冷冻干燥样品横截面的形貌观察结果均一致，都表明糙米酚可抑制淀粉的糊化回生，且抑制程度随酚含量增加而加强，可能原因是淀粉在热处理过程中，糙米酚亲水性羟基与淀粉形成氢键、范德华力等非共价相互作用，改变了淀粉分子晶体与非晶体间的耦合力，阻碍了淀粉双螺旋结构的形成，改变了淀粉分子结构从而使其更难糊化和回生，也使米淀粉消化速率降低。. 综上，糙米酚类物质可抑制消化酶的活性，以及与米淀粉在糊化回生过程中非共价的相互作用，从而降低米淀粉的消化速率。该研究证明糙米酚对米淀粉的消化具有明显的抑制作用。该研究将对有效控制食品中淀粉的消化性质起到推动作用。